A number of aerosol formulations containing pharmaceutical products (both metered and non-metered) exist. However, most of these products contain chlorinated fluorocarbon propellants (CFCs), both individually and in combinations. With the advent of the Montreal protocols, many countries of the world agreed to reduce the use of is “greenhouse effect gases”. CFCs are major contributors to this problem.
Reformulation of topical anesthetic spray compositions to exclude the chlorinated fluorocarbon propellants and still provide an acceptable topical anesthetic spray composition has faced many challenging problems and especially compositions with benzocaine and tetracaine. Along these lines, active benzocaine and tetracaine components need to be dissolved in the composition and exhibit stability over extend periods of time and temperature changes. When the compositions are to be administered by spraying, the compositions must have a viscosity that is low enough for spraying. These properties compete (i.e.-contradictory to each other) with each other making it difficult to find alternative compositions.
The problems are further exacerbated when the composition is to be free from propellants and to minimize the amount of highly volatile components such as ethanol and isopropyl alcohol.
Yet another problem with some current formulations is degradation of the product during packaging.